Redundant power systems are frequently being used to provide steady power for long duration of operation of large systems such as databases and servers. For instance, R.O.C. patent No. M381826 entitled “Redundant power supply apparatus” discloses a power supply apparatus that includes a casing, a back panel, a plurality of power supplies and at least one power input module. The casing has at least one power input housing compartment and a plurality of power output housing compartments. The power input module is held in the power input housing compartment and the power supplies are held in the power output housing compartments. The power input module and power supplies are electrically connected to the back panel. The power input module also is connected to an external power source to receive electric power for the power supplies. Because of multiple power supplies are provided, in the event that one or more of the power supplies malfunction power supply can be maintained without interruption.
R.O.C. patent No. M307787 entitled “Removable composite redundant power system” discloses another type of redundant power system which includes a host holder partitioned into a plurality of main removable compartments, at least one power unit and a plurality of power supplies. The main removable compartments have an inner side with a main power distribution unit located thereon. The power unit has a sub-holder partitioned into a plurality of sub-removable compartments to house the power supplies to form one power unit. Each main removable compartment can hold one power unit. The power units held in the host holder are electrically connected to the main power distribution unit. Each power unit has multiple sets of power supplies. Hence the host holder can continuously provide power in the event that one or more power supplies malfunction.
However, loads supporting remote ON/OFF often have a standby mode. The redundant power system has to provide standby power to the load having the standby mode. R.O.C. patent No. I331714 entitled “Redundant power supply system” discloses a redundant power system supporting the standby mode. It includes a plurality of power supplies each has a standby power unit and a main power unit. The standby power unit continuously outputs power to loads at the power supply standby state so that the loads are waiting to be started at the standby state. It also provides a first power balance unit and a second power balance unit that are connected to the standby power unit and main power unit of a plurality of power supplies to regulate output of two power supplies to achieve a balanced and higher efficiency.
The aforesaid conventional techniques converge power of multiple power supplies and regulate output according to load requirements via a balance circuit, or commonly called a back panel. Please referring to FIG. 1, a back panel 92 is connected to a plurality of power supplies 91. Each power supply 91 provides a main output power 911 and a standby power 912 to the back panel 92 as input. The back panel 92 has a main power bus 921 to converge currents of all the main output power 911, and determines whether the power is sent to loads 941, 942, 943 and 944 at the rear end via remote ON/OFF function of a plurality of starting switches 931, 932, 933 and 934. Similarly, the standby power 912 provided by the power supplies 91 also is converged to a standby power bus 922 of the back panel 92 and directly output to the loads 941, 942, 943 and 944 at the rear end. As the loads 941, 942, 943 and 944 require the standby power 912 whether at the standby or start state, they do not need remote ON/OFF switches.
In practice the architecture shown in FIG. 1 often encounters a problem of inadequate standby power 912. Although output watt of the power supplies 91 increases constantly, it mainly increases output current of the main output power 911 while the rated output current of the standby power 912 remains unchanged. When the standby power required by the loads 941, 942, 943 and 944 connected to the back panel 92 exceeds the capacity of the standby power 912 provided by the power supplies 91, the loads 941, 942, 943 and 944 cannot operate normally. Furthermore, although the capacity of main output power of the power supplies 91 can drive the loads 941, 942, 943 and 944 at the rear end of the back panel 92, and theoretically malfunction or idled for repairs and maintenance of one or more of the power supplies 91 is allowed, due to the loads 941, 942, 943 and 944 are numerous, partial shutdown or malfunction of the power supplies 91 often causes insufficient supply of the standby power 912, and results in abnormal operation of the loads 941, 942, 943 and 944.
Thus inadequacy of standby power limits the number of loads supportable by the power system.